Seafarers versus castaways: reef fishes that cross oceans

raft_fishWhat do coral larvae, lizards, mice and monkey have in common? They all exhibit “rafting” behaviour to get across oceans and seas. Rafting is when animals like these (and many others!) are passively transported on floating objects, like logs and seaweed mats, across open sea. Reef fishes are known have strong preferences for coral and rocky reef habitats, but everyone knows that they also aggregate around floating objects if they find themselves metamorphosing from larvae to juvenile in open sea. Have you ever wondered if rafters who survive long enough to cross oceans are just the lucky ones, or do they have some special traits that make this behaviour possible? In a recent paper in the Journal of Biogeography [link], Osmar and his collaborators have discovered that rafting reef fishes are much more like seafarers than castaways, possessing a set of predictive ecological traits that facilitate this type of oceanic dispersal. For example, large reef fishes that can swim higher above reefs, form schools, and settle in coastal habitats other than reefs are more likely to use rafts to get from one part of the ocean to another than fishes without those traits. What does this mean for humans? Our findings suggest that increasing amounts of plastic litter entering the ocean may differentially influence future rafting opportunities among reef fishes. It seems our plastic litter could, in theory, alter future biogeographic distributions of fishes in the ocean. Less plastic!!